1. Field of the Invention
The present invention relates to a display panel drive-control device and a display panel drive-control method for drive-controlling a display panel such as PDP (plasma display panel) in which a pixel serves as a capacitive load.
2. Description of the Related Art
In recent years, PDP, which has been paid attention as a display panel with a thin size, a large screen and a high definition, comprises a plurality of discharge cells each consisting of scan sustain electrodes arranged in a matrix shape and data electrodes intersecting with the scan sustain electrodes as pixels, and displays an image utilizing emission and non-emission when the discharge cells are discharged.
A general AC-type of PDP panel is provided with a plurality of scan sustain electrodes comprising scanning/sustain electrodes and sustain electrodes which are alternately arranged and a plurality of data electrodes arranged in a direction intersecting in orthogonal state with the scan sustain electrodes. After all of the discharge cells are initialized to be in a same sate by a reset operation, a scanning pulse is applied to the scanning/sustain electrodes. In synchronization with the application of the scanning pulse, a load drive signal, that is a data signal indicating display or non=display, is applied to the data electrodes. In the discharge cells selected in the signal application, wall charges are stored through charging/discharging. These processing are executed to all of the scan sustain electrodes. Next, a sustaining pulse is applied to the scanning/sustain electrodes and the sustain electrodes so that voltage polarities are switched alternately. Accordingly, the wall charges and the sustaining pulse voltage are superposed on each other in the discharge cells where the wall charges are stored, and a full-screen display is performed in such a manner that the light is emitted when a discharge threshold value is surpassed and the light is not emitted when the discharge threshold value is not surpassed. The image is displayed when the foregoing operations are repeatedly executed. Based on the principle of the display described above, it is possible to think that the PDP makes a capacitive load to be a driving target.
In a display panel drive-control device in which the capacitive load is made to be a driving target, it is necessary to realize multiple outputs and drivability with a high voltage in the display panel drive-control device that drives the data electrodes along with the advancements in increasing a screen size, definition and brightness in recent years. However, it is important at the same time to control EMI (electromagnetic interference) and a power supply noise due to the simultaneous change of the high-voltage drive outputs.
As an example of conventional measures for controlling and reducing such unnecessary radiations as the EMI and power supply noise, there is a first conventional example recited in No. 2005-122107 of the Japanese Patent Publications. According to the first conventional example, in a final output drive circuit of an output transistor comprising a high-potential side output element (PMOS transistor) and a low-potential side output element (NMOS transistor) in high-voltage circuit, a capacity is inserted between a connection point where the PMOS transistor and the NMOS transistor that are serially connected to constitute an inverter, and a gate of the PMOS transistor so that influences based on variation of driving load are fed back to the gate input. As a result, any acute change in a waveform of a load drive signal can be controlled.
Further, there is a second conventional example recited in No. 2005-176298 of the Japanese Patent Publications. According to the second conventional example, in a final output drive circuit comprising a Pch transistor and an Nch transistor in high-voltage circuit, an NMOS transistor connected to a gate of the Nch transistor is conducted so as to make the falling edge of the waveform of the load drive signal moderate. As a result, the generation of any noise can be controlled.
However, in the first conventional example wherein a drive load capacity changes depending on a size of the panel, it is necessary to provide capacity cells having a large capacity in view of a load due to the panel, which significantly increases a circuit area in the case of such a constitution that comprises wiring patterns intersecting with one another. Further, special capacity cells are needed because variability of the capacity cells influences a quality of the display, and a process that is different from a standard process is demanded.
The second conventional example, wherein the capacitive load which is not necessarily to be controlled is consequently controlled because the control is solely based on a state of a pixel signal to be displayed, results in an over-spec performance which unnecessarily makes the waveform of the load drive signal too dull.